I could look you could look he could look we could look you could look they could look
V-ing form
I could be looking you could be looking he could be looking we could be looking you could be looking they could be looking
Perfect
I could have looked you could have looked he could have looked we could have looked you could have looked they could have looked
V-ing perfect
I could have been looking you could have been looking he could have been looking we could have been looking you could have been looking they could have been looking
Negation
Simple form
I couldn't look you couldn't look he couldn't look we couldn't look you couldn't look they couldn't look
V-ing form
I couldn't be looking you couldn't be looking he couldn't be looking we couldn't be looking you couldn't be looking they couldn't be looking
Perfect
I couldn't have looked you couldn't have looked he couldn't have looked we couldn't have looked you couldn't have looked they couldn't have looked
V-ing perfect
I couldn't have been looking you couldn't have been looking he couldn't have been looking we couldn't have been looking you couldn't have been looking they couldn't have been looking
Interrogative form
Simple form
could I look? could you look? could he look? could we look? could you look? could they look?
V-ing form
could I be looking? could you be looking? could he be looking? could we be looking? could you be looking? could they be looking?
Perfect
could I have looked? could you have looked? could he have looked? could we have looked? could you have looked? could they have looked?
V-ing perfect
could I have been looking? could you have been looking? could he have been looking? could we have been looking? could you have been looking? could they have been looking?
Interro-negative form
Simple form
couldn't I look? couldn't you look? couldn't he look? couldn't we look? couldn't you look? couldn't they look?
V-ing form
couldn't I be looking? couldn't you be looking? couldn't he be looking? couldn't we be looking? couldn't you be looking? couldn't they be looking?
Perfect
couldn't I have looked? couldn't you have looked? couldn't he have looked? couldn't we have looked? couldn't you have looked? couldn't they have looked?
V-ing perfect
couldn't I have been looking? couldn't you have been looking? couldn't he have been looking? couldn't we have been looking? couldn't you have been looking? couldn't they have been looking?